Automated QA checks: Validate changelog is up to date

[alafanechere]

Tell us about the problem you're trying to solve

We want to make sure each connector has an up to date changelog matching the latest declared version.
We want to run this check as part of the automated QA check that runs in the /test command (see #21699)

Describe the solution you’d like

• Implement and test the check_changelog_entry_is_updated defined here

You can copy / import the existing code from https://github.com/airbytehq/airbyte/blob/master/tools/bin/ci_check_dependency.py#L140